go/vcs: report correct directory for 'no version control'

Apply golang/go@b99fdb2a11ae58834a2c0c646f54d0a587dd269c.

Updates golang/go#6175.
Helps golang/go#11490.

Change-Id: I897bac1bac94b53e950cb5cf5e572d25a7c5996b
Reviewed-on: https://go-review.googlesource.com/21342
Reviewed-by: Andrew Gerrand <adg@golang.org>
1 file changed